A number of options are being considered Enlarge Image

The Forth Tunnel Action Group argue a tube tunnel laid across the estuary is less expensive and more environmentally friendly than a replacement bridge.

Forth Tag made its case for an underwater crossing instead of a new bridge to councillors on Tuesday.

Government transport agency Transport Scotland said it a Forth crossing feasibility study was under way.

Forth Tag argues that placing a tube tunnel in a trench across the bed of the Forth would be cheaper and less damaging on the environment than a new bridge.

When this is complete at the end of May, we will have full details on crossing options at the three corridors that were selected in February Transport Scotland spokeswoman

Engineer John Carson, of Forth Tag, said: "The tunnel will cost at least half the bridge costs and if you look at it on a whole life maintenance basis a tunnel would cost about �3.25m to maintain over 20 years.

"Feta currently spends �10m a year on this bridge. They have just cancelled or delayed a contract to paint the bridge at �76m so you can imagine a second bridge would be as costly to maintain.

"Tunnels cost next to nothing to maintain."

Forth TAG claim they have strong local support for a tunnel crossing but it will be several months before a final decision is made about whether the new Forth crossing will be built above or below the water.

Ministerial reports

Alastair Andrew, FETA general manager, said: "We support the need for an additional Forth crossing and believe that, for longevity and sustainability, this should be a multi-modal crossing with dedicated capacity for public transport.

"Various studies conducted over the past two decades have indicated that the cheapest and least environmentally damaging way of delivering such a crossing would be a suspension bridge alongside the existing one at Queensferry.

"However, we recognise that there is more work to be done. We have full confidence in the studies that Transport Scotland's engineering consultants are now conducting and we look forward to seeing their recommendations."

A spokeswoman for Transport Scotland said: "Our feasibility study into the Forth replacement crossing is still on-going.

"When this is complete at the end of May, we will have full details on crossing options at the three corridors that were selected in February.